Linked from

The 17 pages that link to Pope Gregory XIII, each with the reason it gives.

• Gregorian calendarRelated: His 1582 papal bull established the calendar and its initial date changes.

• Leap yearRelated: His reform reduced leap days to correct the Julian calendar’s accumulated drift.

• CalendarRelated: His reform corrected the Julian calendar's accumulating seasonal drift.

• Calendar reformRelated: His authority launched the reform that corrected Julian calendar drift.

• Solar calendarRelated: His decree launched the calendar reform that bears his name.

• Accademia di San LucaRelated: His pontificate saw the academy’s formal development under papal patronage.

• Christopher ClaviusRelated: He authorized the reform that Clavius explained and defended.

• Lavinia FontanaRelated: His papacy helped sustain Bologna’s religious and civic institutions that commissioned art.

• AprilRelated: His calendar reform is the source of April’s current civil-calendar setting.

• Cologne WarRelated: The papacy backed the Catholic effort to prevent Cologne’s conversion.

• Giacomo della PortaRelated: His papacy brought Della Porta prominent architectural commissions in the city.

• History of calendarsRelated: His decree initiated the most widely adopted international calendar reform.

• Pope Urban VIIRelated: Castagna served as a diplomat and cardinal during Gregory XIII’s pontificate.

• New YearRelated: His calendar reform retained January 1 as the start of the year.

• Year (calendar)Related: His decree introduced the calendar system used for most civil years today.